Method for connecting pipes for high pressure fluids

ABSTRACT

Connection elements include a coupling defining an internal channel having an end segment possessing an insertion opening for insertion of an endpiece and provided with members for retaining the endpiece in leaktight manner therein. The members include an annular axially compressible sealing element that is mounted in the coupling to have one face serving as a bearing surface for a terminal face of the endpiece, and an annularly-shaped retaining element elastically deformable in a radial direction that is received in an inner groove ( 21 ) of the end segment to have an inner circumferential portion projecting through an opening of the inner groove so as to be received in an outer groove of the endpiece. The inner groove has a concave frustoconical flank beside the opening of the end segment to form members for shrinking the retaining element, and a convex frustoconical flank on its side remote from the opening.

The present invention relates to means for connecting ducts of circuitelements for conveying fluids, in particular at high pressures. Theseelements may be constituted by a pipe, a fluid emitter member such apump, or a fluid receiver member such as a cylinder.

Connection devices are known comprising a coupling which is designed tobe mounted on a first fluid transport circuit element and which definean internal channel having a first end segment in communication with theduct of the circuit element and a second end segment, oppositetherefrom, which is arranged to receive an endpiece secured to a secondcircuit element such as a pipe. The second end segment is provided withmeans for holding the endpiece thereto in leaktight manner, said meanscomprising an annular retaining element that is elastically deformablein the radial direction and that, at rest, possesses an inside diameterno greater than the outside diameter of the endpiece, and that it isreceived in a groove of the second endpiece. On its side adjacent to theopening for inserting the endpiece into the second end segment, thegroove has a flank that is frustoconical, and on its opposite side ithas a flank that is radial, with the flanks being spaced apart from eachother in such a manner that the retaining element is axially movablebetween a position close to the radial flank in which it can besubjected to radial expansion in order to allow the endpiece to passthrough while it is being inserted into the coupling, and a positionclose to the opening in which the frustoconical flank forms means forshrinking the retaining element onto the endpiece when an extractionforce is exerted thereon.

That retention technique provides strength against pulling out that islarge even when the pressure of the fluid flowing in the circuit ishigh. Nevertheless, when the circuit is initially put under pressure,the endpiece moves backwards until the retaining element comes into itsposition close to the opening. Successive variations in pressure tend togenerate back-and-forth movements of the endpiece (pistoning) thatencourage leaks or seepage to occur through the coupling. In addition,reversal of the endpiece presents the drawback of forming a zone inwhich fluid is retained between the terminal face of the endpiece andthe internal shoulder of the coupling that forms the abutment againstthe endpiece being pushed into the coupling.

It would therefore be advantageous to have means suitable forrestricting reverse movement of the endpiece relative to the coupling.

The invention provides connection means comprising a coupling definingan internal channel having an end segment possessing an insertionopening for insertion of an endpiece and provided with means forretaining the endpiece in leaktight manner therein, said meanscomprising an annular sealing element that is axially compressible andthat is mounted in the coupling to have one face serving as a bearingsurface for a terminal face of the endpiece, and an annularly-shapedretaining element that is elastically deformable in a radial directionand that is received in an inner groove of the end segment in order tohave an inner circumferential portion projecting through an opening ofthe inner groove so as to be received in an outer groove of theendpiece, the inner groove having a concave frustoconical flank besidethe opening of the end segment to form means for shrinking the retainingelement, and a convex frustoconical flank on its side remote from theopening, which flank is spaced apart from the concave frustoconicalflank by a distance such that the retaining element is received withclearance in the inner groove, and the terminal face of the endpiece andthe outer groove thereof being spaced apart by a distance slightlygreater than the distance between the face of the sealing element andthe opening of the inner groove of the coupling.

Thus, while the endpiece is being inserted into the coupling, theendpiece pushes the annular retaining element against the convexfrustoconical flank which tends to hold the retaining element close tothe concave frustoconical flank, while still allowing the retainingelement to expand elastically in the radial direction. Thus, as soon asthe outer groove of the endpiece comes into register with the opening ofthe inner groove of the coupling, the retaining element returns into itsrest state and its internal circumferential portion projects into theouter groove of the endpiece. Because the distance between the groovesis different from the distance between the face of the sealing elementand the terminal face of the endpiece, the sealing element iscompressed, and pushes against the endpiece in such a manner that theretaining element is clamped between the concave frustoconical flank ofthe inner groove of the coupling and the opposite flank of the outergroove of the endpiece. Reverse movement of the endpiece is thusrestricted.

In a particular embodiment, the outer groove of the endpiece has aconvex frustoconical flank beside a terminal face of the endpiece, saidflank co-operating with the concave frustoconical flank of the innergroove of the coupling to form an angle that is open towards theinsertion opening, which angle is preferably about 10°.

Particularly effective retention of the endpiece in the coupling is thusobtained. In particular, closure of the retaining element in the outergroove of the endpiece is encouraged by the facts that the outer grooveof the endpiece has a convex frustoconical flank facing the concavefrustoconical flank of the inner groove of the coupling, and the convexflank has an angle that is greater than that of the concave flank of theinner groove of the coupling.

According to a preferred characteristic, the retaining element is asplit ring having chamfer-shaped ends on the inside of the split ring.

The risk of the split ring scratching the outer surface of the endpieceduring insertion thereof into the coupling is thus limited.

Other characteristics and advantages of the invention appear on readingthe following description of a particular and non-limiting embodiment ofthe invention.

Reference is made to the accompanying drawings, in which:

FIG. 1 is a cutaway perspective view of connection means in accordancewith the invention;

FIG. 2 is an enlarged view in longitudinal section of the zonereferenced II in FIG. 1;

FIG. 3 is an enlarged view in longitudinal section of the zonereferenced III in FIG. 1;

FIG. 4 is a view analogous to FIG. 3 showing the use of a disconnectiontool with the disconnection means of the invention; and

FIG. 5 is a view of the adjacent ends of the split ring used in theinvention.

The connection means in accordance with the invention that are describedherein are for implanting in a hydraulic circuit to connect a pipe to aninternal duct of a member in the circuit.

With reference to the figures, the connection means in accordance withthe invention comprise a coupling given overall reference 1 comprising atubular body 2 which defines an internal channel 3 and which has a firstend 4, in this case a threaded end for screwing into tapping formed atthe end of the internal duct in the member, and a second end 5 where theinternal channel 3 opens out via an opening 6 through which an endpiece8 is to be inserted into an end segment 7 of the internal channel 3.

The endpiece 8 is tubular in shape having an outside diameter that isslightly smaller than the inside diameter of the end segment 7. Theendpiece 8 possesses an end counterbore 9 with an inside surface 28 thatflares towards the front face of the endpiece from an end defined by aconvex frustoconical surface forming a shoulder 10. Opposite from theend counterbore 9, the endpiece 8 possesses an end that is not visiblein the figures and that is arranged for mounting on one end of the pipe.

The internal channel 3 of the body 2 is provided with means forretaining the endpiece 8 therein in leaktight manner.

The leaktight retaining means comprise an annular sealing element, givenoverall reference 11, that is received in a housing formed at the end ofthe end segment 7 of the internal channel 3.

The sealing element 11 has a ring 12 connecting it to the housing. Thering 12 possesses a radial face projecting axially from which thereextends a terminal sleeve 13, and opposite from the terminal sleeve 13,it possesses an outwardly-chamfered annular portion 14 which is pressedagainst a surface of complementary shape in the housing.

The ring 12 includes means for clipping it into the housing. In thiscase, these means are formed by an annular bead 15 projecting radiallyoutwards from the ring 12 into an annular cavity of the housing.

The outside diameter of the terminal sleeve 13 lies between the minimuminside diameter and the maximum outside diameter of the counterbore 9,and is of a length that is slightly longer than the length of thecounterbore 9. The terminal sleeve 13 possesses an end face 16 that isconcave and frustoconical in order to cooperate with the internalshoulder 10, and it is provided on the outside with grooves 17.

The radial face of the projecting ring 12 from which the terminal sleeve13 extends has a plane groove 27 which surrounds the terminal sleeve 13in order to receive the end of the endpiece 8.

By way of example, the sealing element 11 may be made of a thermoplasticelastomer of the polyurethane type (TPU) or an elastomer of theacrylonitrile butadiene type (NBR), possibly containing a fill ofreinforcing fibers such as glass fibers.

The leaktight retaining means further comprise a split ring 18 havingends 19 that are provided with chamfers 20 on the inside of the splitring (see FIG. 5). The split ring is elastically deformable in a radialdirection, and at rest it possesses an inside diameter that is nogreater than the outside diameter of the endpiece 8.

The split ring 18 is received in a groove 21 of the end segment 7.Beside the opening 6, the groove 21 has a concave frustoconical flank22, and on its side remote from the opening 6 it has a convexfrustoconical flank 23. The flanks 22 and 23 of the groove 21 are spacedapart by a distance that is slightly greater than the diameter of thesplit ring 18 so as to be able to receive it with clearance and formingan angle of about 40° with the central axis of the end segment 7.

The split ring 18 is designed to be received in an outer groove 24 ofthe endpiece 8 in its inner circumferential portion, the inside diameterof the split ring 18 at rest thus being smaller than the outsidediameter of the endpiece 8. The outer groove 24 is defined laterally byflanks 24.1 and 24.2, and at least the flank 24.1 that is situatedbeside the terminal face of the endpiece 8 and which is thus oppositefrom the opening, forms an angle of about 50° relative to the centralaxis of the endpiece 8.

The leaktight retaining means also comprise an O-ring 25 received in agroove 26 formed in the end segment close to the opening 6. The insidediameter of the O-ring 25 is slightly smaller than the outside diameterof the endpiece 8.

In order to connect the pipe fitted with the endpiece 8 to the memberfitted with the coupling 1, the endpiece 8 is inserted into the endsegment 7 of the internal channel 3 via the opening 6.

The endpiece 8 is inserted by force into the O-ring 25 and pushes thesplit ring 18 against the flank 23 of the groove 21. The flank 23 tendsto open out the split ring 18, thus making it easier for the endpiece 8to pass therethrough.

The terminal sleeve 13 of the sealing element 11 penetrates into the endcounterbore 9 of the endpiece 8 until the end face 16 of the terminalsleeve 13 comes into abutment against the internal shoulder 10 of theendpiece 8, and the end face of the endpiece 8 presses against the ring12. The split ring 18 is then received in the outer groove 24 of theendpiece 8, and the sealing element 12 tends to push the endpiece 8 backso that the flank of the outer groove 24 opposite from the opening 6pushes the split ring 18 back against the flank 22 of the groove 21. Itshould be observed that the distance between the groove 24 and theterminal face of the endpiece 8 is slightly greater than the distancebetween the bottom of the plane groove 27 and the opening of the groove21. As a result, a first distance between the terminal face of theendpiece 8 and the point of contact between the split ring 18 and theflank 24.1, and a second distance between the bottom of the plane groove27 and the point of contact of the split ring 18 against the flank 22,differ by an amount such that-the ring 12 is axially compressed when thesplit ring 18 is received in the groove 24, thereby keeping the splitring 18 in contact with the flanks 24.1 and 22. The flank 22 then exertsa shrinking force on the split ring 18, which closes into the groove.The co-operation between said flank of the outer groove 14, the splitring 18, and the flank 22 opposes extraction of the endpiece 8 from thecoupling 1. Thus, beside the terminal face of the endpiece 8, the convexfrustoconical flank 24.1 of the outer groove 24 of the endpiece 8co-operates with the concave frustoconical flank 22 of the inner groove21 of the coupling 1 to form an angle α that is open by about 10°towards the insertion opening 6 (i.e. the apex of this angle α issituated beside the sealing element 11) which encourages closure orshrinkage of the split ring 18 into the outer groove 24 when anextraction force is exerted on the endpiece 8.

The fact that the terminal sleeve 13 is slightly compressed, as is thering 12, increases the contact force between the end face 16 and theinner shoulder 10. In particular because of the correspondingfrustoconical shapes of the end face 16 and of the inner shoulder 10,the risk of the end face 16 escaping from bearing against the innershoulder 10 is small, and the outer surface of the terminal sleeve 13 ispressed against the inner surface of the end counterbore 9. Because ofits shape and its dimensions, the inner surface 28 exerts a prestressforce on the terminal sleeve 13 which is forced to bear against thissurface. In addition, co-operation between the frustoconical shapes ofthe inner shoulder 10 and of the end face 16 associated with thecompression force encourages the terminal sleeve 13 to be deformed intoa barrel shape serving to press the inner sleeve 13 against the insidesurface 28.

The end of the endpiece 8 is received in the plane groove 27. The planegroove 27 subdivides the radial face of the ring 12 into an innerannular portion (extended by the terminal sleeve 13), and an outerannular portion which receives the end of the endpiece 8, thus servingto hold the sealing element 11 in position. This plane groove 27 extendssubstantially in register with the bead 15 so that inserting theendpiece 8 into the plane groove 27 tends to support the ring 12,thereby opposing any escape of the bead 15 from the annular cavity ofthe housing.

When the circuit is put under pressure, the fluid tends to press thechamfered portion 14 against the adjacent surface of the housing and theterminal sleeve 13 against the inside surface 28, thereby reinforcingsealing.

It should be observed that the inclination of the flanks 24.1 and 22also makes it possible to avoid these surfaces being subjected topeening.

In order to disconnect the endpiece 8 from the coupling 1, it ispossible to use a tool 50 constituted by a bushing that is splitlongitudinally so as to enable it to be put into place laterally ontothe endpiece 8. The bushing has one end arranged to be slid between theoutside surface of the endpiece 8 and the inside surface of the portionof the end segment 7 that extends between the opening 6 and the flank22, so as to be inserted into the split ring 18 and/or so as to push thesplit ring 18 back against the flank 23, while the opposite end of thebushing is provided on the outside with a collar enabling it to bepushed into the coupling.

Simultaneously with pushing in the tool 50, a traction force is appliedto the endpiece 8.

Naturally, the invention is not limited to the embodiment described butalso covers various embodiments coming within the ambit of the inventionas defined by the claims.

In particular, the endpiece can be fitted onto the end of a pipe as inthe embodiment described, or the endpiece may be formed by the end of apipe that is arranged accordingly.

In a variant, the terminal face of the terminal sleeve 13 and theshoulder 10 of the end counterbore 9 can also be formed by radialannular faces. The terminal sleeve 13 may also be of a length that isshorter than that of the end counterbore 9 of the endpiece 8 so that thecoupling is sealed only by contact between the outside surface of theterminal sleeve 13 and the inside surface of the end counterbore 9.

The sealing element may be of a configuration different from thatdescribed, for example it need not have a terminal sleeve 13.Furthermore, the endpiece 8 need not have an end counterbore 9 or couldhave an end counterbore 9 with an inside surface that is vertical or ofany other circularly cylindrical shape.

1-4. (canceled)
 5. Connection means comprising a coupling (1) definingan internal channel (3) having an end segment (7) possessing aninsertion opening (6) for insertion of an endpiece (8) and provided withmeans for retaining the endpiece in leaktight manner therein, said meanscomprising an annular sealing element (11) that is axially compressibleand that is mounted in the coupling to have one face serving as abearing surface for a terminal face of the endpiece, and anannularly-shaped retaining element (18) that is elastically deformablein a radial direction and that is received in an inner groove (21) ofthe end segment in order to have an inner circumferential portionprojecting through an opening of the inner groove so as to be receivedin an outer groove (24) of the endpiece, wherein the inner groove has aconcave frustoconical flank (22) beside the opening of the end segmentto form means for shrinking the retaining element, and a convexfrustoconical flank (23) on its side remote from the opening, whichflank is spaced apart from the concave frustoconical flank by a distancesuch that the retaining element is received with clearance in the innergroove, and wherein the terminal face of the endpiece and the outergroove thereof are spaced apart by a distance slightly greater than thedistance between the face of the sealing element and the opening of theinner groove of the coupling.
 6. Connection means according to claim 5,wherein the outer groove (24) of the endpiece (8) has a convexfrustoconical flank beside a terminal face of the endpiece (8), saidflank co-operating with the concave frustoconical flank of the innergroove of the coupling (1) to form an angle that is open towards theinsertion opening.
 7. Connection means according to claim 6, wherein theabove-specified angle is about 10°.
 8. Means according to claim 5,wherein the retaining element is a split ring (18) having chamfer-shapedends (19) on the inside of the split ring.